The invention relates to a connecting element for two machinery components or constructional components, in particular fitting anti-fatigue bolts, fitting threaded bolts or the like, having a threaded portion used for fastening and an anti-fatigue portion arranged axially displaced to the threaded portion and consisting of several elevations and grooves, with the minor diameter of the grooves of the anti-fatigue portion being made smaller than the minor diameter of the threaded portion. As a fitting anti-fatigue bolt, the connecting element can be provided with a head. As a fitting threaded bolt, a tightening screw thread is expediently provided in addition.
A connecting element of the type described above is known from German Offenlegungsschift No. 21 43 784. In this connecting element, the anti-fatigue portion is also made as a thread which is first of all made with an outside diameter which is larger than the outside diameter of the threaded portion. However, this outside diameter of the anti-fatigue shank is rough worked to the fitting dimension. This connecting element is manufactured by thread rolling, that is by cold working, with the run of the material grain not being disturbed. The minor diameter of the grooves in the anti-fatigue portion can be between 2 and 10% smaller than the minor diameter of the fastening thread of the threaded portion. This known connecting element has a large elastic extension, so that the elasticity of the anti-fatigue portion is increased compared with the threaded portion. During uninterrupted stressing, a possible fracture will in all probability occur in the fastening thread in the known bolt. This printed matter contains no references on the configuration of the pitch diameter in the anti-fatigue portion nor on the configuration of the stress cross-section in the anti-fatigue portion.
A connecting element which is subjected to axial and bending stress is known from German Offenlegungsshrift No. 22 33 560, which connecting element likewise has an anti-fatigue and a threaded portion for fastening. In this connecting element the minor diameter of the grooves of the anti-fatigue portion depends on the material properties and the requisite elastic length under the effect of the axial force. This connecting element is also manufactured by a rolling operation. The groove and elevation volumes in the anti-fatigue portion are the same. The outside diameter of the elevations corresponds to the value determined by the design size. The profiling of the rounded parts of the grooves in the anti-fatigue portion is larger than or the same as the rounded parts of the fastening thread in the threaded portion. Here, too, no details are given on the dimensioning of the pitch diameter of the anti-fatigue portion of elevations and grooves.
From German Utility Model No. 83 25 206.1, a connecting element is known in which the minor diameter of the grooves of the anti-fatigue portion corresponds to the minor diameter of the fastening thread in the threaded portion. The two minor diameters are therefore the same, so that the resilience in the area of the anti-fatigue portion cannot be greater than the resilience in the threaded portion. The outside diameter of the elevations in the anti-fatigue portion can be larger than the outside diameter of the fastening thread of the threaded portion. An improvement in the properties by such a configuration can therefore only be expected to a very limited extent.